Process for waste plastic recycling

ABSTRACT

An apparatus for recycling or decompstiong waste plastic is decomposed in a diluent such as hot oil through actions involving free readical precursors, such as polyvinyl chloride or polyurethane is achieved at low temperatures. The thermal decompostion (or pyrolysis) reaction is for about 1 hour at 375° C. annd usable products, such as distillate, coke and oil are recovered. Additonally the diluent my ber recycled within the apparatus.

This is a national stage application of PCT/US94/02433, filed Mar. 8,1994.

I. TECHNICAL FIELD

The present invention relates generally to processes for low temperaturethermal decomposition of waste plastics. Specifically, the inventionfocuses upon achieving decomposition of waste plastics at a lowertemperature than was previously possible. In particular municipal,health and industrial waste plastics are processed such as (but notlimited to) polyethylene (PE), polypropylene (PP), polystyrene (PS),polyethylene terephthalate (PET), polyurethane (PU), and polyvinylchloride (PVC).

II. BACKGROUND ART

Waste plastics, that is synthetic polymer-containing substances, pose anenvironmental issue because of the problems associated with disposal: alarge volume of non-biodegradable material. Because of the limits onlandfill capacity, future recycling or decomposition is a necessity.Direct recycling back to the manufacture is not always feasible becausesuch waste plastic is often mixed with respect to polymer type andseparation is uneconomical. Economical considerations for processingwaste plastic often require the use of the unseparated mixed wasteplastic. Plastic recycling originated with the manufacture of syntheticthermoplastics. Rejected parts, trim, and flash from operationsrepresented valuable materials that were ground and recycled with virginmaterial. This process was potentially repeated a number of timesprovided the percentage of regrinds remained low. As long as the plasticscrap generated by the industry was clean and uncontaminated with otherplastics, reprocessing within the industry continued to expand, providedthe price of virgin plastic remained high. After 1960 with a decrease inprices, profit margins for plastic scrap were squeezed, and disposalinstead of reprocessing often occurred.

After 1970, plastic prices rose again due to OPEC raising the cost ofpetroleum feedstocks and recycling practices again increased. Interestincreased not only in processes for reclaiming waste plastics, such asproduct evaluation for chemicals and fuels, but also in the necessarystep of separation of plastics from other waste material. A review ofthis early history of plastics recycling is given by R. J. Ehrig inPlastics Recycling, Oxford University Press, N.Y., 1992, hereinafterreferred to as Ehrig (1992). Some of the early operating plants forrecycled plastic included a Department of Energy funded plant inLaPorte, Tex., which used a fluidized bed of sand and was designed for17 million pounds per year of atactic polypropylene. It ran from1980-82. In 1984 at Ebenhausen, Germany, a 20 million pound per yearplant used molten salt with a fluidized bed reactor to process plasticwastes and tires.

In all cases economics governed whether such plants continued operation.Since 1985 plastics recycling has become more economically feasible dueto continued plastics technological growth and increased environmentalconcern, however, significant cost impacts remain due to the level ofthe elevated temperatures previously required.

III DISCLOSURE OF INVENTION

The present invention relates to a process which overcomes theabove-mentioned deficiencies in the prior art and to a process whichachieves decomposition of waste plastic at a relatively low temperature.As one example, the process decomposes a mixed stream of waste plasticat a temperature generally less than 375° C. in a hot oil medium. Theprocess converts the polymeric structure of the waste plastic orplastics to smaller chemical molecules such as the monomeric units andrelated chemical structures at a relatively lower temperature. It alsoserves the market for the such products. Since this market is not ato-be-developed manufacturing process, but rather one for which existingplants in the refining and petrochemical industries already exist, theprocess is adaptable to existing facilities that are alreadyexperiencing limited supplies of low molecular weight, heteroatomic freefeedstocks from petroleum crude oils. The low-molecular weightdistillate from waste plastic processing according to this invention mayhelp reduce the demand for imported petroleum products and help decreaseour dependence on foreign crude oil.

Basically the process is one in which the materials to be reacted areadded or controlled so as to assure the existence of sufficient orappropriate amounts of free radicals. These free radicals are includedto initiate free radical chain depolymerization reactions known to"unzip" polymer structures. To avoid recombination and to furtherenhance the process, this reaction is accomplished in a diluent such asan oil.

IV. BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic diagram of a system for processing recycledwaste plastic according to one technique of the present invention.

V. BEST MODE FOR CARRYING OUT THE INVENTION

The subject invention processes or decomposes mixed waste plastic at arelatively very low temperature. It may use thermal degradation in anoil media. Typical thermal degradation of waste plastics, such as thatassociated with municipalities waste, has previously required 400°-600°C. Through the present invention, this may occur at below about 375° C.This represents a saving of energy requirements and capital costs. Inbasic form, the invention is a process for the low-temperature thermaldecomposition of waste plastics by a free radical mechanism attemperatures below 375° C. This may be accomplished in a diluent such asoil. This diluent does not significantly impact the action of the freeradicals, serves to maintain energy levels, reduce chemical interaction,and serves as a diluent so as to avoid recombination of reactiveproducts. As those skilled in the art could readily ascertain, the freeradicals are neutral, unpaired electron shell substances which initiatethe process and may be provided by a free radical precursor. Theseprecursor substances are essentially all substances capable of providingfree radicals at the condition chosen for the reactant. As those skilledin the art would also readily understand, they may include certainplastic resins (ie. polyvinyl chloride, polyurethane, and most likelynylon 66) and almost any other materials which produce the freeradicals, such as those materials containing carbon-carbon,carbon-nitrogen, carbon-oxygen, or carbon-sulphur bonds as well someother compounds which may be free radical initiators and which do notvolatilize too quickly in the reacting conditions chosen. The freeradical precursors may exist as part of the waste plastic, may be aseparately added substance, or may even be added to the diluent. Thelow-temperature activity of the present invention is believed to beattributed to the free radical chain depolymerization reactions known to"unzip" synthetic polymer structures. The free radical(s) liberated frompolyvinyl chloride or from other sources at temperatures below 375° C.act as initiators to start the process. In an oil, free radicals fromthe initiator attack the polymer structure to satisfy their electronicstructures. This results in the abstraction of a proton from the polymermolecule which initiates the free radical process in the polymer chainto break the structure into smaller molecules. The result isdecomposition of the plastic at temperatures lower than previouslyexpected. The resultant products are likely to be a distillate, coke,noncondensable hydrogen, and other gases.

In establishing the preferred embodiment of the invention, it isbelieved that there are three important conditions for low-temperaturethermal decomposition of such plastics to occur. First, the plastic mayneed to be diluted in a diluent such as an oil solution to preventrecombination reactions. Second, if the free radical initiators aregenerated from the waste plastic, the plastics composition must containresin types, such as polyvinyl chloride, that decompose at temperaturesbelow 375° C. to generate free radicals. Third, even though theinitiator concentration must be low, in a continuous process, it appearsnecessary to maintain the level at a critical concentration of about0.5% (wt) to maintain the reaction.

As mentioned, the oil is believed to serve a variety of functions. Inaddition to those previously mentioned, it may act as a diluent whichlimits termination reactions that produce the higher molecular weightspecies as discussed above. It may also serve as a heat transfer mediato ensure uniform heating of the waste plastics. The nature of the oilutilized in the process does not appear to be critical to many wasteplastic degradation applications, but it may change the technicalprocessing requirements. One choice is used motor oil since it, itselfis a waste material. Yet other oils include but are not limited to heavyoils (that is, oils not distillable at the conditions chosen for thereactant or about 1 atmosphere pressure at up to 400° C.), fluidized bedcatalytic cracker slurry oil, distillation tower vacuum bottoms, andheavy heating or bunker oil.

The stability of the oil at process conditions may impact the ability torecycle the oil as well as the amount of overhead distillate formed. Lowvalue oils, that is oils either high in elements other than carbon andhydrogen oils of high molecular weight, particularly aromaticsubstances, or substances having a low hydrogen to carbon atomic ratiomay also be used. This can afford a significant economic advantage assuch substances are likely to be undesirable for other purposes and maybe readily available at refinery sites. In addition, utilization of lowvalue oils in the process of the present invention can create a resultwhich basically can be characterized as combining two undesirable orwaste materials to create a desirable and useful material.

As mentioned a distillate may be formed. This may include a generalhydrocarbon material whose volatility allows it to become overhead vapormaterial under certain conditions. For the preferred embodiment, thisoccurs at approximately 375° C. under nominal pressure of about oneatmosphere. Importantly, the products of the process may be materialswhich either have economic value and can be utilized in the marketplace, can be consumed by the process, or can be safely released to theenvironment.

For most situations the common range of normal volatility for distillateformed from mixed waste plastics according to this process is about40°-375° C. Higher boiling hydrocarbon materials remain with the heavyoil. The distillate products may contain components that could beclassified as value-added products (ie. toluene and styrene). These arenot usually produced by the present process as pure compounds in thedistillate. Instead they are likely to be present in complex mixtureswith other hydrocarbon species in the preferred embodiment. Naturally,separation may be achieved to obtain these components in pure form. Thismay occur on site if the economics warrant. Alternatively, thedistillate or products may be marketed without additional separation.The whole distillate may have market value as a feedstock to thepetrochemical and refining industries. The use of these distillates orproducts in the refining industry is attractive because the types ofcompounds present indicate they might be useful as octane additives forthe production of unleaded gasoline. The aromatic compounds (toluene,ethylbenzene, etc.), and the branched and cyclic structures are known tohave relatively high octane numbers which can be used to enhance theoctane rating of gasoline.

Five waste plastics may be considered as often included in a typicalwaste plastic stream. These are polyethylene (PE), polypropylene (PP),polystyrene (PS), polyethylene terephthalate (PET), and polyvinylchloride (PVC). Thayer reported a distribution for municipal wastes ofPE: 63%, PS: 11%, PP: 10%, PET: 7%, PVC: 5%, Other: 4%; See Solid WasteConcerns Spur Plastic Recycling Efforts, Chemical & Engineering News,p7, Jan. 30, 1989; hereinafter Thayer (1989). By ignoring the remaining4%, this information produced the basis for one common mixed wasteplastic experimental composition.

FIG. 1 shows a typical process system in schematic form. The raw mixedwaste plastic is supplied by a first supply 10 and is fed to amechanical chopper 11 which produces a chopped up, or comminuted,plastic material 12. This chopped mixed waste plastic 12 enters a lockhopper 20 or some mixer which may mix it with a diluent supplied by asecond supply 25. It may also store the mix and meter it 21 into asolution tank 22 that is well stirred or mixed 23 (potentiallycontinuously) and has an appropriate amount of diluent such as oil fromsecond supply means 25 or from recycling mixed with it at about 200° C.The lock hopper 20 may include some type of star valve to prevent theescape of vapor. Further, the solution tank 20 may be utilized to assurethat the plastic is solubilized in the heavy oil that is recycled tothis tank from farther through the process. The oil flux through thistank may thus be maintained to allow sufficient residence time in thetank to solubilize the plastic.

The oil may be cycled through from further down the process and mayadditionally contain a selected amount of new oil 47. The ratio of oilto plastic may not be critical but a range of from about 2:1 to 10:1 oilto plastic appears to work. This solution of oil and plastic 24, may bestirred 23 at all times. The system may have an injected free radicalprecursor 32 which may enter the reaction container 41 at some solutioncontroller 40. This may include some type of controllable valve and mayalso include some type of controlling logic 33. This may act to controlthe content of the solution to assure that it will contain a sufficientfree radical content when heated so that substantially all waste plasticis decomposed. The free radical precursor 32 may be injected when neededby monitoring (such as by a sensor) and sensing (such as by a sensor)the conditions within the reaction container 41. If the overhead 43decreases sufficiently (most likely sensed by an increase in thereactant temperature ascertained or a decrease in the amount of heatneeded to maintain a given reactant temperature), it likely indicatesthat the relative amount of free radical precursor has dropped so morefree radical precursor 32 may be automatically added. (Naturally, onlythe relative proportions are involved so one could conversely hold theamount of free radical precursor 32 steady and adjust the amount ofwaste plastic.)

Preferably the free radical precursor 32 is chosen to decompose at orbelow the nominal reactor temperature into some free radical or freeradicals. Thus, acceptable free radical precursors include polyvinylchloride, polyurethane, and other materials that will thermally formfree radicals at temperatures at or below the reaction temperatureselected. These free radical precursors may be stored is some thirdsupply 31 until use and may even be waste plastic themselves.

The reaction container 41 may be well stirred 42 and may have enteringthe solution of oil, plastic, and precursor material, cycled back heavyoil 44, and some new heated oil 45. Again, the residence time in thereactor or reaction container may be maintained to maximize plasticsconversion. Further, product gas may be recycled through the head spaceof the reactor to aid in removing volatiles from the reaction zone.

As shown, the reactor heavy oil 46 leaves and passes through amultipurpose heat exchanger or temperature controller 48 (such as aheater) where it is heated or cooled depending upon conditions ofoperation and leaves 49 to be pumped 50, cycled back 44, exited 51, orfed to the solution tank 22. This residual heavy oil may suffer somethermal degradation and may contain a portion of the plastic degradationthat is not thermally decomposed. Thus, some heavy oil may be discharged51 and fresh oil 47 inserted. In many instances the amount of oil orheavy oil recycled with a recycling element 44 may be in the range ofapproximately 70-90 percent, preferably about 80-85 percent, of thereactor fluid. Yet the process will usually work with a heavy oilrecycle amount from zero to about 95 percent. Zero, or no, heavy oilrecycled means a straight through flow process.

The multipurpose heat exchanger 48 may act as a regenerative heater forthe fresh oil 47, which may be preheated by the recycled heavy oilentering 46 and leaving 49, before entering 45 the reaction container41. It also may serve to heat the reactor heavy oil as heavy oil recycle44 to keep the reaction temperature adequate. This normally has a rangeof about 300°-375° C. This heating operation can involve a heat sourcesuch as steam, burned fuel, fuel from the overhead gas 60, or coke andother solids formed from plastic decomposition and subsequentlyrecovered material.

The reactor overhead 43 potentially consists of three components: anoncondensable overhead gas 60, a condensable liquid stream of overheaddistillate 64 that is collected and stored 65, and condensable overheadspecialty decomposition substances 66. Thus the condenser 61 or somecollector means can be two-staged. The first stage may condense, perhapsin a modified cyclone arrangement, any such overhead specialtydecomposition substances. These are usually solid 66, and largely comefrom PET degradation. The second stage may operate with cooled water 62which then leaves 63 and condenses the overhead distillate 64, the majorprocess product. Thus the amount of PET in the mixed waste plastic maygovern how much solid is potentially present and collected. Also a smallamount may be handled by becoming entrapped in the heavy oil 51. Theoverhead gas 60 may pass though the condenser 61 unaffected; however,before further use it can be water scrubbed to remove HCl or otherhalide acids.

Various equivalent flow sheets are possible and that shown in FIG. 1 isonly one of many potential that could carry out the subject invention.

EXPERIMENT 1

Before mixed plastic wastes were studied, each individual componentplastic was thermally decomposed to have a basis for the differencebetween mixed and individual resource recovery, and whether the mixedplastic wastes when thermally decomposed had an unexpected interaction.

The thermal decomposition was performed in hot fresh oil, usually attemperatures between 375° and 450° C., as a convenient substance thatdissolved the plastics. Further, used or waste motor oil was aconvenient fresh oil source and in itself represented a waste product.Other fresh oils that were mostly stable below 450° C. were employedsuch as fluidized bed catalytic cracker Slurry oil, distillation towervacuum bottoms, and heavy heating or bunker oil. For convenience, moststudies employed a simulated used or waste motor oil which was SAE 50motor oil.

A laboratory setup was used for preliminary experimentation whichconsisted of a thermally regulated flask with water condenser. The flasktemperature was regulated to within 5° C. and the overhead distillatecondensed with 16° C. water while the amount of uncondensed overhead gaswas measured. The SAE 50 oil and the appropriate plastic resin wereplaced into the flask and the flask was purged with nitrogen beforeheating began. After the proper time at temperature, the flask wasquenched.

The range of temperatures was 375° to 450° C. for most plastics;however, PVC and PET were too reactive at these temperatures and theirrange was reduced to 285° to 360° C. The reaction time varied up to onehour in 15 minute increments.

The important individual results which varied with the type of plasticwere as follows:

PE: With 75% oil and 25% PE starting and a 45 minute operating time,little overhead distillate was condensed below 425° C. but here 9.0% ofthe total product mix was overhead distillate. At 450° C. 28.6% wasdistillate indicating some of the original oil had been decomposed.Heavy oil containing some decomposition products remained in the flask.For all temperatures no measurable coke was produced and the overheadgas was less than 2.5%. For the time varying experimentation at 425° C.,the overhead distillate increased with time peaking at 11.3% at onehour. A gas chromatography/mass spectrometry detailed study of the 425°C. overhead distillate indicated over 64 organic compounds and the 15%majority was classified as a mixture of C₄ substituted cyclopentanes.

PP: With 75% oil and 25% PP starting and a 45 minute operating time,little overhead distillate was condensed below 400° C. but here 9.5% ofthe total product mix was distillate. At 425° C. 14.9% was distillatewith apparently minuscule oil decomposed. Heavy oil containing somedecomposition products remained in the flask. For all temperaturesinvestigated no measurable coke was produced, and the overhead gas wasless than 2.0%. For the time varying experimentation at 425° C., theoverhead distillate increased with time peaking at 18.6% at one hour. Agas chromatography/mass spectrometry detailed study of the 425° C.overhead distillate indicated over 55 identified organic compounds andthe 5.9% majority was identified as 1,4 pentadiene with a close secondat 5.3% classified as C₄ substituted octane.

PS: With 75% oil and 25% PS starting and a 45 minute operating time,little overhead distillate was condensed below 390° C. but here 7.0% ofthe total product mix was overhead distillate. At 425° C. 33.7% wasoverhead distillate indicating some of the oil had been decomposed.Heavy oil containing some decomposition products remained in the flask.For all temperatures no measurable coke was produced and the overheadgas was less than 1.5%. For the time varying experimentation at 400° C.,the overhead distillate increased with time peaking at 18.9% at onehour. A gas chromatography/mass spectrometry detailed study of the 400°C. overhead distillate indicated over 49 identified organic compoundsand the large 33.2% majority was identified as styrene.

PVC: With 89% oil and 11% PVC starting and a 45 minute operating time,little overhead distillate was condensed even at 360° C., the maximumtemperature employed, but here only 1.2% of the total product mix wasoverhead distillate. Heavy oil containing some decomposition productsremained in the flask. For all temperatures coke production increasedwith temperature and was 7.8% at maximum temperature. Except for HCl,overhead gas production was always minimal. HCl production was constantat 6.1% with no temperature variation and apparently most chlorineappeared in this form.

PET: With 86% oil and 14% PET starting and a 45 minute operating time,no overhead distillate was condensed. At 375° C., the maximumtemperature employed, a Solid product of 7% of the total product mix wasobtained, and this was likely terephthalic acid and/or benzoic acid.This solid product sublimed and collected largely in the flask neckmaking the material balance less accurate. Heavy oil containing somedecomposition products remained in the flask. For all temperatures cokeproduction decreased with temperature and was 15% at 325° C. but only 6%at 375° C. Overhead gas production was always minimal.

EXPERIMENT 2

A review of the tests in Experiment 1 indicated that the apparentoptimum temperature for hot oil decomposition of PE and PP was about425° C., about 400° C. for PS, about 375° C. for PET, and about 325° C.for PVC. Thus a temperature staging process was employed with mixedwaste plastic, often called mixed resins. However PET was not employedin this experiment since its solid decomposition product tended to clogthe apparatus. A further aspect in omitting PET was that recent trendsin recycling of waste plastic have been to separate out the bottles madeof PET and recycle them directly to the bottle manufacturer.

A three stage temperature experiment was performed using 270° C. for 20minutes, 410° C. for 30 minutes, and 450° C. for 45 minutes. The oil tomixed resins ratio was ten to one. The selected reactant mixed resinswere proportioned to the amounts reported by Thayer (1989). Threedifferent combinations of oil and sweep gas were employed, SAE 50 oilwith and without nitrogen sweep gas, and fluidized bed catalytic crackerslurry oil with nitrogen sweep gas. The results are presented in Table 1where the products section for distillate was the incremental distillateproduced at that temperature. The total distillate was the sum of alldistillate produced during the experiment. By summing over eachexperiment temperature, the cumulative distillate production wasobtained. The heavy oil product represented the remaining input oil pluswhat product compounds remained dissolved in it.

Referring to Table 1, at all temperatures much of the SAE 50 oil wasdecomposed, and this large amount was unexpected from the results foundfrom the individual components in Experiment 1. Evidently a free radicalwhich promoted decomposition was occurring for even at the lowesttemperature, 270° C., the results of Experiment 1 indicated only PVCwould decompose. Thus, the free radicals produced from PVC appeared toinitiate the decomposition reaction of PE, PP, and PS, and as well asfor the SAE 50 oil.

For the slurry oil experiment the free radical only affected the mixedresins as the slurry oil apparently did not decompose even at 450° C.Further the mixed resins essentially decomposed completely at the lowesttemperature of 270° C. A further favorable aspect was that no measurablecoke was formed with this slurry oil.

                  TABLE 1                                                         ______________________________________                                        Material Balances for the Experiments Investigating                           Temperature-Staged Thermal Decomposition of Mixed Plastics                    ______________________________________                                        Sweep Gas    None       Nitrogen Nitrogen                                     Oil          SAE 50     SAE 50   Slurry Oil                                   Stage I, °C.                                                                        270        270      270                                          Stage II, °C.                                                                       410        410      410                                          Stage III, °C.                                                                      450        450      450                                          Reactants                                                                     Oil, g       100.00     100.00   87.45                                        PVC, g       0.60       0.60     0.44                                         Polystyrene, g                                                                             1.20       1.20     0.97                                         Polypropylene, g                                                                           1.10       1.10     0.88                                         Polyethylene, g                                                                            7.10       7.10     5.55                                         Total, g     110.00     110.00   95.29                                        Products                                                                      Heavy Oil, g 27.08      18.82    89.25                                        Total Distillate, g                                                                        74.90      81.04    5.62                                         at 270° C.                                                                          17.06      12.44    5.61                                         at 410° C.                                                                          14.95      33.77    0.01                                         at 450° C.                                                                          42.89      34.83    0.00                                         Hydrochloric acid, g                                                                       0.32       0.32     0.23                                         Coke, g      2.88       2.12     0.00                                         Gas, g       3.44       7.70.sup.a                                                                             0.11.sup.a                                   Total, g     108.62     110.00   95.21                                        Closure, %   98.7       100.00   99.9                                         ______________________________________                                         .sup.a Gas production determined by difference                           

EXPERIMENT 3

It appears from the previous experiments that sufficient free radicalswere needed to enhance the rate of decomposition at the lowtemperatures. Thus, if the fraction of PVC was insufficient in the mixedwaste plastic to generate enough free radicals, some source ofadditional free radical was added. The control mechanism for the processwas based upon this action. Since the decomposition reactions werehighly endothermic, if insufficient free radicals were present whenadequate mixed resins were dissolved, the temperature of the system rosebeyond the normal targeted 375° C., and further the amount of distillateformed decreased significantly. To compensate, an additional source offree radicals was added to bring down the temperature and increase thedistillate production. Extra free radical precursor up to about 10% ofthe waste plastic mix did not adversely affect the process.

This suggested that operating under about 375° C. was feasible todecompose the mixed resin and that the time factor was not critical. Thefresh oil source is believed not crucial in many applications andapparently any available high-boiling oil that was processable byrefinery operations was potentially usable.

The process can employ a wide range of input waste plastics ranging frompure PE, PP, PS, PET, and PVC, along with adequate free radicalprecursor added. Likewise any convenient mixture of such mixed plasticswas usable as input to the process. Thayer (1989) reported that fourpercent of municipal waste plastic fell into an other category and wasnot separately identified. Yet this other category appeared processableby the subject invention since even if it did not decompose, it remainedin the residual heavy oil. Further if it formed solids, recovery waswith the coke and likely burned. Thus a separate group of mixed wasteplastic is defined as `other waste plastic` and consists of all otherplastic types besides PE, PP, PS, PET, and PVC.

The products from this process have potential depending upon economics.These are in general overhead gas, overhead distillate, overheadspecialty decomposition substances, residual heavy oil, and halideacids. The overhead distillate may potentially feed refinery stocks.Overhead gas may be burned for energy to heat the oil, or if not needed,may be flared. The halide acids, preferably hydrogen chloride, may berecovered as largely hydrochloric acid. The overhead specialtydecomposition substances may be largely decompositions from PET, such asterephthalic acid and benzoic acid and may have good commercialpotential if purified. The residual heavy oil and any coke may beburned. Products that are cycled back and burned to provide heat for theprocess are referred to as burnable products.

The foregoing discussion and the claims which follow describe apreferred embodiment of the present invention. Particularly, withrespect to the claims, it should be understood that changes may be madewithout departing from the essence of the invention. In this regard itis intended that such changes would fall within the scope of the presentinvention. It simply is not practical to describe and claim all possiblerevisions to the present invention which may be accomplished. Forinstance, the claims are directed to both methods and apparatus.Although each have been included in various detail, they represent onlyinitial claims directed toward only some basic aspects of the invention.The various permutations and combinations of the claims presented and ofother aspects disclosed in the specification are intended to beencompassed within the claims and should be understood to be supportedby the existing disclosure. Naturally, the disclosure of processes ormethods should be construed to address apparatus utilized to achievesuch processes or methods and should be construed to support a fullscope of method and apparatus claims. While these may be added toexplicitly include such details, the existing claims should be construedto encompass such aspects. In addition, the present disclosure should beconstrued to encompass subclaims similar to those presented in aprocess, method and apparatus context.

In addition, to the extent any revisions utilize the essence of theinvention, each would naturally fall within the breadth of protectionencompassed by this patent. This is particularly true for the presentinvention since its basic concepts and understandings are fundamental innature and can be broadly applied. The foregoing description of thespecific embodiments so fully reveal the general nature of the inventionthat others can, by applying current knowledge, readily modify or adaptfor various applications to suit specific applications. Such embodimentswill not depart from the generic concept, and therefore should be deemedto fall within the meaning and range of equivalents of the disclosed andclaimed embodiments. It should also be understood that the phraseologyand terminology herein is for the purpose of description and not oflimitation.

We claim:
 1. A system for decomposing waste plastic comprising:a. afirst, second, and third supply wherein said first supply supplies wasteplastic and said second supply supplies oil; b. a mixer responsive to atleast two of said supplies; c. a reaction container connected to saidmixer and responsive to said third supply; d. a heater connected to saidreaction container, e. a collector connected to said reaction container;and f. a solution controller wherein said third supply is responsive tosaid solution controller.
 2. A system for decomposing waste plastic asdescribed in claim 1 wherein said oil is selected from the groupconsisting essentially of waste motor oil, fluidized catalytic crackerslurry oil, distillation tower vacuum bottoms, heavy heating or bunkeroil, or combinations thereof.
 3. A system for decomposing waste plasticas described in claim 1 wherein said heater achieves temperatures of nomore than 400° C.
 4. A system for decomposing waste plastic as describedin claim 2 wherein said solution controller is responsive to thetemperature within said reaction container.
 5. A system for decomposingwaste plastic as described in claim 1 wherein at least one of saidsupplies is adapted to assure appropriate amounts of free radicalcontent when heated in a solution.
 6. A system for decomposing wasteplastic as described in claim 5 wherein at least one of said supplies isadapted to assure appropriate amounts of free radical precursor.
 7. Asystem for decomposing waste plastic as described in claim 5 furthercomprising a sensor adapted to ascertain an amount of free radicalslikely to be present in said solution after said solution is heated. 8.A system for decomposing waste plastic as described in claim 7 whereinsaid sensor is adapted to sense a reactant temperature of said solution.9. A system for decomposing waste plastic as described in claim 1further comprising a recycling element adapted to recycle a portion ofsaid oil.
 10. A system for decomposing waste plastic as described inclaim 9 wherein said portion is from 0 to 95% of said oil.
 11. A systemfor decomposing waste plastic as described in claim 9 wherein saidportion is from 70 to 90% of said oil.